Atrial fibrillation is the most common sustained arrhythmia and may increase the heart rate to, and in excess of, 100 to 175 beats per minute. It is associated with a high incidence of symptoms (e.g., atria quiver rather than contracting normally) and with multiple medical sequelae including strokes, blood pooling in the atria, and the formation of blood clots.
Recently, clinical investigators have found that in many cases, atrial fibrillation is initiated, and possibly maintained, by electrical triggers located in the pulmonary veins, Haissaguerre M, Jais P, Shah D C, Takahashi A, Hocini M, Quiniou G, Garrigue S, Le Mouroux A, Le Metayer P, Clementy J.; Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins; N Engl J Med. 1998; 339(10):659-66. It also has been suggested that this can be cured or greatly suppressed by electrically isolating the pulmonary veins from the left atrium, Haissaguerre M, Jais P, Shah D C, Garrigue S, Takahashi A, Lavergne T, Hocini M, Peng J T, Roudaut R, Clementy J.; Electrophysiological end point for catheter ablation of atrial fibrillation initiated from multiple pulmonary venous foci; Circulation 2000; 101(12):1409-17.
A variety of different atrial fibrillation treatment techniques are available, including drugs, surgery, implants, and catheter ablation. While drugs may be the treatment of choice for some patients, drugs typically only mask the symptoms and do not cure the underlying cause. Anti-arrhythmia drugs are disclosed, for example, in U.S. Pat. Nos. 4,558,155, 4,500,529, 4,988,698, 5,286,866 and 5,215,989. Also, the treatment of atrial arrhythmia by pharmaceuticals has been described in a number of medical articles and books including, for example, Martin, D., et al., Atrial Fibrillation, pgs. 35-41 (1994); Falk, R. H., et al., Atrial Fibrillation (1992); Singer, I., et al., Clinical Manual of Electrophysiology (1993); and Horowitz, L. N., Current Management of Arrhythmias (1991).
Implantable devices, on the other hand, usually correct an arrhythmia only after it occurs. See, for example, U.S. Pat. Nos. 5,282,836, 5,271,392 and 5,209,229 and Martin, D., et al., Atrial Fibrillation, pgs. 42-59 (1994) as to the use of an implanted atrial defibrillator or cardioversion. Implants, however, require a surgical procedure to be performed to install the implant, along with the risks associated with such procedures.
Surgical and catheter-based treatments, in contrast, can cure the problem by electrically isolating the ectopic foci responsible for the atrial fibrillation. An example of such a surgical procedure for the treatment of atrial arrhythmia is the “Maze” procedure that is discussed in Cox, J. L. et al., Electrophysiology, Pacing and Arrhythmia, “Operations for Atrial Fibrillation,” Clin. Cardiol. Vol. 14, pgs. 827-834 (1991). See also Cox, J. L., et al., “The Surgical Treatment of Atrial Fibrillation,” The Journal of Thoracic and Cardiovascular Surgery, Vol. 101, No. 4, pgs. 569-592 (April, 1991), and Cox, J. L., et al., “The Surgical Treatment of Atrial Fibrillation,” The Journal of Thoracic and Cardiovascular Surgery, Vol. 101, No. 4, pgs. 406-426 (March, 1991). Other surgical procedures for atrial arrhythmia are discussed, for example, in Martin, D., et al., Atrial Fibrillation, pgs. 54-56 (1994).
In the catheter based treatments, atrial fibrillation is addressed or treated by ablating the abnormal tissue or electrically active tissue responsible for the atrial fibrillation (i.e., electrically isolating the accessory pathway responsible for the atrial fibrillation). The catheter-based treatment techniques rely on the application of various destructive energy sources to the target tissue, including direct current electrical energy, radio frequency electrical energy, laser energy, thermal (heat) energy (resistive element), cryo-thermal (cold) energy and the like. The ablation energy source, such as an ablating electrode, is normally disposed along a distal portion of the catheter.
A variety of catheter-based ablation strategies have been pursued to effect electrical isolation of the pulmonary veins. In such ablation strategies, electrophysiologists contemplate forming or placing ablative lesions at the pulmonary vein ostia, or even in the left atrium proper (see Pappone C, Rosanio S, Oreto G, Tocchi M, Gugliotta F, Vicedomini G, Salvati A, Dicandia C, Mazzone P, Santinelli V, Gulletta S, Chierchia S., Circumferential radiofrequency ablation of pulmonary vein ostia: A new anatomic approach for curing atrial fibrillation. Circulation, 2000; 102(21):2619-28).
Initially, electrophysiologists used standard radiofrequency (RF) ablation catheters to place a sector or ring of lesions inside the proximal segment of these veins. This technique was found to be problematic because success was limited due to the frequent incidence of arrhythmic triggers located at the pulmonary vein ostia (proximal to the ablative lesions), and the procedure carried an unacceptably high complication rate due to the subsequent development of pulmonary vein stenosis. Several catheters have been developed to apply circumferential lesions just inside the pulmonary veins using RF energy, ultrasound, or thermal energy. Catheters also have been developed to form circumferential lesions on the chamber wall about the pulmonary ostium and/or linear lesions on the chamber wall that extend between adjacent pulmonary veins.
There is found in U.S. Pat. No. 6,012,457 and in U.S. Pat. No. 6,024,740 a device for forming a circumferential conduction block in a pulmonary vein (see FIG. 1A) and a device whereby a circumferential block is formed in a pulmonary vein and a linear lesion is formed between two adjacent pulmonary veins (see FIG. 1B). The devices employ an inflatable balloon to engage the pulmonary vein and to deliver energy in a radially symmetrical pattern to the vein. A guide wire is used to guide the balloon member into the pulmonary vein; however, the inflatable balloon and the ablative energy sources contained within it makes the use of the device complex. Also, while the system expedites pulmonary vein isolation, it is complex to manufacture and does not solve the fundamental difficulties associated with ablating inside the pulmonary veins, listed above.
There is found in U.S. Pat. No. 5,971,983 a device for forming a circumferential block in a pulmonary vein and for forming a linear lesion formed between two adjacent pulmonary veins (see FIG. 1C). The described ablation device includes first and second ends that are bordered by first and second anchors and the anchors are adapted to secure the ablation element ends at predetermined first and second locations along the body space wall. In this way, the ablation device is adapted to ablate an elongate region of tissue between those locations. The anchors may be guidewire tracking members, each including a bore adapted to receive and track over a guidewire (one for each bore), and anchor within adjacent pulmonary vein ostia when the engaged guidewires are positioned within the respective veins. The device uses an inflatable balloon or similar strategies to engage the pulmonary vein and deliver energy in a radially symmetrical pattern. While the system expedites pulmonary vein isolation, it is complex to manufacture and does not solve the fundamental difficulties associated with ablating inside the pulmonary veins, listed above.
There is found in U.S. Pat. No. 5,938,660 devices that use two inflatable balloons to engage the pulmonary vein. For one of the described devices, RF energy is used to ablate the tissue between the balloons. For another of the described devices, the two balloons are inflated to form a seal that isolates the tissues there between and a chemical ablative material is introduced between the two balloons thereby ablating the tissues. The seals formed by the balloons are intended to prevent the chemical ablative material from escaping.
There is found in U.S. Pat. No. 6,325,797 a catheter assembly including a distal portion that forms a substantially closed loop transverse to the longitudinal axis of the catheter body, where at least one electrode is provided along the loop. In use, the loop is axially directed into contact with the chamber wall about the vessel ostium (See FIG. 1D). When the at least one electrode is energized, the electrode ablates a continuous lesion pattern about the vessel ostium so as to electrically isolate the vessel from the chamber.
The goal in such cases is to electrically isolate the pulmonary veins, but to do so with a wider ring of lesions and without placing lesions inside the pulmonary veins themselves. It is, however, technically more challenging to place a set of contiguous lesions in a large ring outside the pulmonary vein than to create a ring of lesions inside the vein. Also for other types of ablation catheters, the ablation catheter tends to fall away from the wall of the left atrium as it is moved from point to point, making contiguity of the lesions difficult to achieve. Procedure times are often long and fluoroscopic radiation exposure can be substantial. Electroanatomical mapping techniques have been used to mitigate these problems, but manipulation of the catheter to the many sites required for creation of large isolating rings of ablative lesions remains challenging, particularly due to the irregular three-dimensional shape and trabeculated endocardial surface of the left atrium.
There is found in U.S. Pat. No. 6,241,728 a left atrium ablation catheter including a deflectable eletrophysiology catheter having ablation electrodes along the tip thereof. It is further described that the electrode tip is sized and configured to create the desired lesion at the target site without movement of the electrode tip along the target site.
A recently introduced ultrasound ablation balloon system is designed to apply a ring of lesions at the pulmonary vein ostium instead of inside the vein (see Meininger G R. Calkins H. Lickfett L. Lopath P. Fjield T. Pacheco R. Harhen P. Rodriguez E R. Berger R. Halperin H. Solomon S B. Initial experience with a novel focused ultrasound ablation system for ring ablation outside the pulmonary vein. J. Interventional Cardiac Electrophysiol. 8:141-148, 2003). This system is complex and will place lesions distal to arrhythmic triggers located peri-ostially.
It thus would be desirable to provide a new device(s) for ablating tissue so as to form lesions as well as systems and methods related thereto. It would be particularly desirable to provide such a device, system, and method which embodies a guide member for localizing the ablation mechanism with respect to the tissue surface and which guide member provides a mechanism by which the ablation mechanism can be easily and continuously repositioned with respect to the tissues (e.g. rotated about the guide member), thereby to form a circumference of such lesions. It also would be desirable to provide such devices that can form such a circumference of lesions more easily and with less risk as compared to prior art devices as well as making continguity of the lesions easier to achieve as compared to prior art devices. Such collection devices preferably would be simple in construction as compared to prior art devices.